Fig. 8.

Example of non-sensory influences on rapid plasticity in speech perception. A The color scale shows categorization of speech as beer or peer across an acoustic space defined by voice onset time (VOT) and fundamental frequency (F0). Each dimension contributes to categorization, and their influence covaries; longer VOT and higher F0 result in categorization as peer, whereas short VOT and lower F0 result in more beer responses. B This same acoustic space can be sampled selectively (yellow-shaded exposure stimuli, canonical) to convey the canonical English covariation of VOTxF0 or an “accent” that reverses the typical English covariation of VOT and F0 (exposure stimuli in light yellow, reverse). Intermixed test stimuli with a perceptually ambiguous VOT and either high (blue) or low (green) F0 reveal how the short-term regularities conveyed by the canonical and reverse stimulus distributions affect the impact of F0 in signaling beer vs. peer. In the context of the canonical English covariation, listeners rely on F0 to categorize the test stimuli as beer versus peer (B, bottom). In the context of the accent conveyed by the reverse covariation of VOTxF0, the influence of F0 is down-weighted such that it no longer signals category membership (B, bottom). C Schematic illustration of the origins of these effects shows sensory input dimensions that represent acoustic dimensions like F0 (illustrated at the top in blue-to-yellow gradient from low to high F0) providing weighted input (more effective inputs are illustrated as thicker lines) to non-sensory native language representations learned across long-term experience with a language community (here, /b/ versus /p/). These weighted inputs to the speech sound representations are interactive and bidirectional allowing for rapid online plasticity of the effectiveness of sensory information in informing speech perception (as in panel B).